In the case of railroad ties it is necessary that rail fastening screws, which determine positioning of the track lie exactly at prescribed positions. This applies particularly to ties for switches is which this position varies from tie to tie.
The position of the rail fastening screws in the cross tie is fixed by means of screw anchors into which the screws are turned, or by means of tubes through which the screws are turned, or by means of tubes through which the screws are passed. The positionally correct assembly of these components for the fastening screws for the rails which continually change position in the cross tie represent a considerable cost factor in the manufacture of cross ties, which one endeavors to keep as small as possible through simplification of the design of these components and their fastening and by shortening of the assembly time. In addition, in cross ties produced in prestressing fixtures, the fastening of the components on the concrete form must not impede the movement of the tie resulting from setting up and prestressing in the form during the manufacturing process.
From FR PS 15 65 510, FIG. 2, a holding fixture is known for a component displaceable from the inner side of the concrete form with a nipple reduced in cross section opposite the retaining pin. This holding fixture has the disadvantage that it is not anchored in the concrete form. In rough handling at assembly it can drop out. During forming it could remain attached to the part being produced, and would have to be removed by a time-consuming post-forming operation from the anchor hole after concreting. Furthermore, it may be subjected to large shear forces between the concrete form and the part being produced when that part changes length during the production process.
Furthermore, an assembly anchor for ties is known from DE 30 39 931 which is connected in one piece to a fastening means of about equal cross section, which can be inserted into a bore of corresponding size in the concrete form. In this fastening means connected to the anchor it is considered a disadvantage that it cannot be recovered. Due to its relatively large cross section the fastening means has such strength that, even when there is a desired breaking point, the intended break does not occur with assurance. At removal of the tie from the form, the anchor thus can remain attached to the bottom of the form, and is pulled out of the concrete.